One of the causes (if not the cause) of bug 56269 is if something
manages to throw an exception that makes it to MediaWiki::run's
last-resort exception catcher while having an open database transaction:
the transaction never gets committed or rolled back, so it gets
implicitly rolled back and a warning is raised.
The API has the opposite problem in bug 63145: it catches the exception
but then does the normal DB shutdown which *commits* the transaction.
This is certainly the Wrong Thing to do.
Ideally, neither of these would ever happen because any code using
transactions would have its own try-catch that would catch any
exception, rollback the transaction, and then rethrow the exception. But
it happens anyway, so let's have both of these last-resort exception
handlers do the rollback, and also log the exception so the throwing
code has a better chance of being properly fixed.
Bug: 56269
Bug: 63145
Change-Id: I8f1da51187b281fe4afc0d5a0c49f5caf3612e92